1. Field of the Invention
The present invention relates to a disc drive apparatus on which a disc cartridge receiving a double-sided recording type disc-like recording medium may be mounted in a reversible manner, and more particularly to a mechanism for opening/closing a shutter provided in a disc cartridge.
2. Description of the Prior Art
An image file system in which an optical disc (including both writable type and rewritable type) is used as a file memory has been noted because its recording density is much larger than that of other information recording mediums. Thus, a variety of disc drive devices and suitable disc cartridges have been proposed for that system.
FIG. 53 is a perspective view schematically showing an example of a disc drive apparatus of this type. A cartridge holder 3 is formed into a frame shape into which a disc cartridge is insertable and has an opening 2, at its bottom, through which a turntable is inserted. Opening/closing arms 4 and 5 are pivotally provided at their ends to side portions on a disc cartridge stop side of the cartridge holder 3. Pins 4a and 5a coupled to these ends of the opening/closing arms 4 and 5 are disposed in a cartridge insertion path within the cartridge holder 3. The opening/closing arms 4 and 5 are normally biased by springs (not shown) in a direction in which the disc cartridge 6 is discharged from the cartridge holder 3. The opening/closing arms 4 and 5 are rotated inwardly (in the directions indicated by arrows A and B) by the insertion of the disc cartridge 6. When the disc cartridge 6 is discharged from the cartridge holder 3, the arms 4 and 5 are automatically returned back to the original positions.
On the other hand, in the disc cartridge 6 adapted to this optical disc drive apparatus, as shown in FIGS. 54 and 55, a window 10 for insertion of the head and the turntable are formed in a portion from a central portion to a front edge 9 of a cartridge half 8 which rotatably receives a two-sided recording type optical disc 7. A shutter 11 is slidably mounted for closing/opening the window 10 along the front edge 9. The two-sided recording type optical disc 7 is formed by bonding two optical disc elements with their recording layers facing each other.
In the front edge 9 of the disc cartridge 6, a sliding portion 12 is recessed for sliding movement of the above-described pins 4a and 5a. Further, a recessed portion 13 contiguous with the sliding portion 12 is formed so that the recessed portion 13 may come into contact with the pin 4a or 5a. Cutouts 14 are formed in sides of the disc cartridge 6 for positioning the disc relative to the cartridge holder 3. At corner portions close to rear edges 15 of the upper and lower halves 8a and 8b (not shown), erroneous erasure preventing mechanisms 16 and 17 are formed in a symmetrical manner with respect to a center line C--C of the window 10.
As shown in FIG. 54, the window 10 is closed by the shutter 11 in the non-use condition of the disc cartridge 6, i.e., the condition in which the disc cartridge 6 is not inserted into the cartridge holder 3. Thus, foreign matter may be prevented from entering through the window to protect the optical disc 7.
When the disc cartridge 6 is inserted into the cartridge holder 3, as shown in FIG. 52, one of the pins 4a is inserted into a space 18 (FIG. 54) defined by the end face of the shutter 11 and the sliding portion 12.
Under this condition, when the disc cartridge 6 is depressed, one of the arms 4 is rotated in the direction indicated by the arrow A in accordance with the depression thereof, so that the pin 4a is engaged with the end face of the shutter 11 to thereby depress the shutter 11 in an opening direction D.
At this time, the other pin 5a is not engaged with the shutter 11 but rides over the front face of the shutter 11 to slidingly move along the front face in the direction indicated by the arrow B.
When the disc cartridge 6 is inserted into the cartridge holder 3 up to a predetermined position, as shown in FIG. 55, the shutter 11 is moved by a predetermined distance in the direction D to thereby open the window 10. At this time, the pin 4a falls in the recess 13 formed in the front edge 9 to thereby position the shutter 11 at the predetermined position.
Simultaneously therewith, a sensor (not shown) provided in the cartridge holder 3 will detect the insertion of the disc cartridge 6 at the predetermined position. The cartridge holder 3 is lowered and the optical disc 7 is clamped on the turntable 1 to thereby complete the loading of the disc cartridge 6.
It should be noted that an example of a conventional cartridges in which a cutout 19 is formed in a front face of a shutter 11, and a pin 4a or 5a is engaged with the cutout to thereby open and close the shutter is shown in FIGS. 56A and 56B.
It is also to be noted that, since a width W of the window 10 of an optical disc cartridge is larger than that of a magnetic disc cartridge (for a floppy disc), the amount of movement of the shutter 11 for opening/closing the window 10 becomes larger.
In order to increase the amount of movement of the shutter 11, it is necessary to increase a length L of the arms 4 and 5 and to decrease an angle .theta. defined between a line E--E connecting the pivot 4b, 5b and the pin 4a, 5a to each other and a line F--F in conformity with the disc cartridge insertion direction (which angle will be referred to as an initial set angle).
However, if the length L of the arms 4 and 5 is increased, there is a disadvantage such that the disc drive apparatus is made large in size. On the other hand, if the initial set angle .theta. is decreased, a collision force generated when the front edge 9 of the disc cartridge 6 is brought into abutment with the pin 4a, 5a is increased, and at the same time, the opening/closing operation of the shutter 11 needs a large force, resulting in degradation in operational feeling.
If the initial set angle .theta. is increased, then it is possible to avoid or suppress the foregoing disadvantage. However, inversely, the amount of movement of the shutter 11 will become small. It is therefore difficult to apply increasing the initial set angle to the optical disc drive apparatus.
Incidentally, in a magnetic disc drive apparatus, there has been provided a structure in which the arms are mounted on an upper surface of the cartridge holder 3 to thereby miniaturize the apparatus as in, for example, Japanese Patent Unexamined Publication 59-2269. However, in this magnetic disc drive apparatus, there is no means for mounting the disc cartridge in a reversible manner. Thus, it is impossible to apply this to the optical disc drive apparatus for driving the two-sided recording type optical disc.
Turning to the apparatus for the disc shown in FIGS. 56A and 56B, since the opening/closing arms 4 and 5 must be crossed during of the shutter opening/closing operation, it is difficult to increase the size of the cutout 19. As a result, the engagement between the cutout 19 and the pin 4a, 5a would be insufficient, so that the engagement therebetween is likely to be released. In particular, in a small size disc cartridge in which the size of the cutout is restricted, such a disadvantage is remarkable. It is impossible to put this system into practical use.